— Scott McNealy, Sun Microsystems Chairman, President and ceo

// generic printing
}
}
Report
runReport()
printReport()
runReport()
buzzwordCompliance()
superclass methods 
(including the overridden 
runReport()
A reference to the subclass object 
(BuzzwordReport) will always call 
the subclass version of an overridden 
method. That’s polymorphism. 
But the subclass code can call 
super.runReport() to invoke the 
superclass version.
If method code inside a 
BuzzwordReport subclass says:
the runReport() method inside 
the superclass Report will run
superclass version of the 
method does important stuff 
that subclasses could use
call superclass version, 
then come back and 
do some subclass-
specific stuff

---

interfaces and 
polymorphism
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229
 BULLET POINTS
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When you don’t want a class to be instantiated (in other words, you don’t 
want anyone to make a new object of that class type) mark the class with the 
abstract 
keyword.
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An abstract class can have both abstract and non-abstract methods.
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If a class has even one abstract method, the class must be marked abstract.
$
An abstract method has no body, and the declaration ends with a semicolon (no 
curly braces).
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All abstract methods must be implemented in the first concrete subclass in the 
inheritance tree.
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Every class in Java is either a direct or indirect subclass of class Object (java.lang.
Object).
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Methods can be declared with Object arguments and/or return types. 
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You can call methods on an object only if the methods are in the class (or interface) 
used as the reference variable type, regardless of the actual object type. So, a 
reference variable of type Object can be used only to call methods defined in class 
Object, regardless of the type of the object to which the reference refers.
$
A reference variable of type Object can’t be assigned to any other reference type 
without a cast. A cast can be used to assign a reference variable of one type to a 
reference variable of a subtype, but at runtime the cast will fail if the object on the 
heap is NOT of a type compatible with the cast.
Example: